I don't really have an answer other than wait and see, but from personal experience, I usually have 3-4 days of fertile CM before I actually ovulate, so if you DTD CD12, then didn't ovulate until day 16 or 17, you are probably fine.
Mirena can screw up your cycles for a little while after it is out. I had periods every two weeks, then just spotting, then really long cycles. Eek on the falling out! I was always a little worried about that. If it's been 13 days, you're likely to test positive by now if you were pregnant, but definitely should by tomorrow.
My Mirena fell out too, but I never really got regular periods while on it. Your cycle probably wasn't regular? About 2 months after mine came out (I had it in starting 6 weeks postpartum, then for about 1.5 years) my periods came back and were perfectly on schedule.